Key Engineering Materials Vol. 968

Abstract: Synchrotron X-rays have the advantage of being a micro beam, allowing us to create detailed stress maps. However, due to a dendritic structure, measuring the residual stresses of a welded part is difficult. This challenge is caused by the difference in the positions of the diffracted crystal grains. To address this problem, we proposed a double exposure method. In this presentation, the double exposure method was applied to measure the residual stress of the plate that was cut from the welded pipe. Detailed strain maps under a plane stress state were obtained. Conversely, the residual stress distributions of the welded pipe under a triaxial stress state were measured using neutrons. From these results, the detailed stress maps of the root part of the butt-welded pipe were made up by the complimentary use of the synchrotron X-rays and neutrons. The results can significantly explain theinitiation and propagation of stress-corrosion cracking. We name this analysis method the quantum beam hybrid stress analysis.

Abstract: The X-ray stress measurements by the sin²ψ method, the cos α method and the XRD² method are basically composed of the fundamental equations based on diffraction vectors and the calculation for determining X-ray stress. The fundamental equations are expressed differently, which are due to the fact that the measurement systems associated with the incident X-ray control device and the diffracted X-ray detector are different. Although the dependent variable that is the measured quantity is the same diffraction angle theta in the fundamental equations, the main independent variable is different like the tilt angle ψ in the sin² ψ method and the central angle α, γ of the Debye-Scherrer ring in the cos α method, the XRD² method, respectively. Therefore, the stress determination method has been devised based on each the fundamental equation. By clarifying the differences between each X-ray stress measurement method and making a relationship, a unified representation for the fundamental equations is formalized. Therefore, a comparison of each X-ray stress measurement method is expressed in the same Euler space, and a conversion method for each X-ray stress measurement method is presented.

Abstract: Jominy end quench test is a standardized metallurgical experiment for obtaining data on steel hardenability. Construction of numerical simulation of the test provides a way for parameterizing and validation of numerical models using the experimental data. In the current work we present the coupled heat transfer, conduction and phase transformation model, which allows for calculation of phase fractions at different positions at the Jominy test piece, and includes the latent heat released by the phase transformations. Also, the temperature and phase fraction dependence of the thermal conductivity is included in the calculation.

Abstract: Mechanical spectroscopy (MS) is a dynamic technique for the characterization of material properties providing information that can not be obtained otherwise, and is important for a variety of engineering fields. To illustrate the potentiality of MS, this work provides some examples regarding different metallic systems: (i) thin Al foils for MEMS, (ii) complex structures of point defects in Cr martensitic steels for structural applications in future nuclear fusion reactors, (iii) depinning of dislocations from point defects and precipitates.

Abstract: Today, Atomic Layer Deposition (ALD) sets the limits for achieving nanometer precision of thin, yet almost dense films. However, the initial growth process, determining possible film thinness, is poorly understood. A better understanding can be obtained with the help of in-situ characterization during film growth with high spatial and chemical resolution. Transmission Electron microscopy (TEM) would be a suitable and widely available technique to accomplish this objective. However, standard instruments have differing vacuum requirements than those necessary for ALD. During ALD, TEM detectors could be damaged as they are being exposed to corrosive volatile chemical compounds. Here we present a dedicated TEM holder design, where ALD deposition occurs inside a microchip containing a large area cavity surrounded by thin film Al₂O₃ membranes. These membranes act as windows for TEM characterization while decoupling the ALD process from the TEM environment. The microchip consists of longitudinal large overhang shell structures, themselves made by ALD and etched in an HF vapor etch processes. The set-up, which includes controlled heating, was tailored to ALD requirements, and passed a vacuum-pressure test. Post-mortem inspection of film growth on a silicon sample chip demonstrates the successful formation of an ALD Al₂O₃ film with 40 nm thickness inside the cavity. These results demonstrate the potential of the system to enable a range of experiments on growth phenomena that may lead to even thinner films and better control of interfaces than previously possible.

Abstract: The role of non-metallic inclusions is gaining increasing attention in steel research. Various inclusion characterisation techniques and methods are utilised in order to obtain reliable and accurate results. Automatic inclusion measurements carried out using field-emission scanning electron microscope with energy dispersive spectroscopy produces a large amount of data about detected inclusions in the scanned area. The data obtained must be processed and analysed in one way or another, for example, to classify the inclusions or construct size distributions. Until now, a Matlab script has been used to determine the phase composition of inclusions, and to classify them accordingly. The Matlab script has acted as the basis for the recently developed Karakterizer tool, written in Python. In addition to less restricted use, the recent advances include a graphical user interface. This paper demonstrates the use of Karakterizer tool in characterising inclusions with examples of direct-quenched martensitic steels with a yield strength of 1000 MPa.

Abstract: The main aim of this work is to develop an automated system for sample preparation. For the detection of small amounts of biological material, methods and procedures for concentration must be used. In this case, sample preparation refers to the concentration of bacteria in solutions. The problem of automated concentration of microbiological substances of low concentration in solution is discussed in more detail in this work. During sampling, volumes of approximately 100 mL are taken and processed. To achieve this goal, the construction of an automated system was planned and implemented. This system without contamination of the sample was implemented using a peristaltic pump, pinch valve, and air bubble detector. The influence of different system parameters has been investigated and the function of the system was tested for suitability in laboratory experiments. In addition, results from laboratory tests were evaluated. It was shown that a concentration of samples is possible with the help of a filter and backwash process. From this it is evident that an automated setup for this process should be aimed at, to make the procedure possible for non-specialized personal in this field. Furthermore, human error should additionally be minimized compared to all manual laboratory test. This study demonstrates such a system and shows the potential of filtering and backwashing of bacteria.

Abstract: Typically, samples for PCR instruments are prepared manually by trained laboratory personnel, which in this case refers to the sample preparation, the dispensing of a master mix and a biological sample with subsequent mixing. To reduce the workload, there are approaches towards fully automated PCR systems, but in most cases only proprietary thermal cyclers can be used. Other approaches involve a similarly complex robotic solution. In this work, the spectrum was extended by a method that can be integrated into the workflow of existing PCR protocols. For this purpose, a user-friendly solution using a microfluidic chip was developed. For the sample preparation different mixing concepts were selected as well as a concept for aliquoting. Optimization and evaluation were assisted by utilization of simulations to study system behavior. The systems consisting of a mixer and a flow splitter were manufactured by milling. Subsequently, the mixing and aliquoting capability of the system could be investigated in the laboratory assembly. The testing of this prototype showed moderate results which are attributed to the accuracy of the laboratory assembly.

Abstract: Dynamic modulus vs. temperature was measured in different alloys (stainless steels, Al alloys, Ti alloys, Ni-base superalloys) prepared by additive manufacturing and an anomalous trend was observed in some of them. Dynamic modulus, measured in successive mechanical spectroscopy test runs with heating-cooling cycles, exhibits an anomalous trend in the first test run that is no longer present in the successive runs. The phenomenon consists in the inversion of the decreasing trend of modulus occurring during heating and gives rise to its permanent increase at the end of the complete heating-cooling cycle. The temperature range where the modulus anomaly takes place and the permanent increase observed after cooling depend on the specific alloy. Scanning electron microscopy (SEM) observations and density measurements revealed that the irreversible process causing the anomalous behavior is the closure of pores of nanometric size leading to material densification. This result has been discussed by considering lattice diffusion.